This invention relates to hydrophilizing a hydrophobic intraocular lens (IOL). Contact lenses are known and are worn exterior to the eye and are usually removed for a period daily. Intraocular lenses are made of materials similar to those used for contact lenses, for example polymethylmethacrylate (PMMA), silicone rubber or other suitable transparent polymeric material. Contact lenses are often hydrophilized by various methods to reduce irritation, and equally are softened by various methods for the same reason to reduce irritation. Although hydrophobic materials and hard materials cause irritation, the irritations are not equivalent, and the methods of softening and hydrophilizing are not equivalent.
Intraocular lenses are inserted into the eye to replace the natural lens, which typically has become opaque, for example due to cataract development in a patient. The natural lens is surgically removed, through an incision at the edge of the cornea, then the intraocular lens is inserted into the anterior or posterior chamber of the eye. Irreversible damage may be caused to the endothelium cells of the cornea, it they are touched by a hydrophobic surface, such as the lens or surgical instruments. As the intraocular lens becomes a permanent fixture in the eye, it is strongly desirable to dehydrophobize or hydrophilize the surface of the lens to circumvent this destruction. One approach is to coat the lens with a material which renders the surface hydrophilic, such as polyvinylpyrrolidone, methylcellulose, polyvinylalcohol and even guar gums, using a coating solution. Similar treatments have been used for contact lenses, see for example U.S. Pat. No. 3,183,152, issued May 11, 1965 to Szekely et al., teaching a treated polyvinylalcohol for contact lenses. Similar coatings are taught for intra-ocular lenses, in the following articles:
by H. E. Kaufman et al.,
Endothelial Damage from Intraocular Lens Insertion. Inv. Opth. Vol 15 pp 996-1000 (1976).
Prevention of Endothelial Damage from Intraocular Lens Insertion. Tr. Am. Acad. Opth. & Otol. Vol 83 pp 204-212 (1977).
Pathology of the Corneal Endothelium. Inv. Opth. Visual Sci. Vol 16 pp 265-268 (1977).
Corneal Endothelium Damage with Intraocular Lenses: Contact Adhesion Between Surgical Materials and Tissue. Science Vol 198 pp 525-527 (1977).
by P. U. Fechner,
Methylcellulose in Lens Implantation. J. Am. Intraocular Implant Soc. Vol 3 pp 180-181 (1977).
by P. M. Knight et al. in U.S. Pat. Nos. 4,170,043 and 4,170,661, both issued Oct. 9, 1979.
All these teach or suggest coating the intraocular lens with a suitable hydrophilic material. While some of these coatings may be effective in reducing damage to the corneal endothelium cells during surgery (especially if used within 30 minutes after treatment) they quickly disperse and leave the surface once the IOL is in the eye thus returning the lens to its original hydrophobic state.
The trauma of surgery generates protein in the vitreous fluid (of the eye) which can deposit on hydrophobic surfaces and thus coat the IOL rendering it less transparent. As it is known that coatings cannot prevent such protein adsorption, other solutions have been adopted, which include making the lens entirely of hydrophilic plastic such as hydroxyethylmethacrylate or grafting a hydrophilic polymer to a PMMA lens. The former solution results in an unstable lens which tends to distort with time whereas the latter solution, though potentially effective, adds considerably to the cost of the lens. There is consequently a need for a method of permanently hydrophilizing the surfaces of intraocular lenses.